In modern computer systems, vast amounts of data may need to be accessed by hundreds, thousands or even million of different entities, including persons and groups (e.g., organizations) of persons. Accordingly, computer systems have been developed in which data is stored on multiple physical storage units (PSUs), i.e., physical storage devices including, but not limited to magnetic tape, disk drives, solid state storage devices (e.g., flash drives) or portions thereof. Typically, these physical storage devices are grouped together as part of one or more data storage systems (e.g., storage arrays), for example, data storage systems made available by EMC Corporation, headquartered in Hopkinton Mass. (“EMC”).
Entities typically access the data on such data storage systems via one or more host systems for which communication paths have been established over one or more communication media (e.g., as part of a network) between ports of the host systems and ports of the data storage systems. Through the host systems, data of the data storage system may be accessed and modified using I/O operations, for example, read and write operations. To this end, data storage systems may provide storage services to host systems. Data storage systems may include PSUs, which typically are nonvolatile memory on which data is persisted even if power is lost, and cache memory (i.e., caches), which typically is volatile memory in which data is temporarily stored for efficiency purposes. Typically, data can be read from, and written to, cache faster than it can be from the non-volatile PSUs. Data storage systems typically include front-end logic and functional components to handle the exchange of data between data storage system ports and cache, and back-end logic and functional components to handle data exchanges between the cache and the PSUs.
Host systems typically do not address the PSUs of the data storage system directly, but rather, access the PSUs by addressing virtual (i.e., logical) storage units (VSUs), for example, logical volumes (LVs), thin devices and storage groups, which hide the details of actual physical storage from the host. A VSU may or may not correspond one-to-one to a PSU.
As data storage capacity, computation and flexibility demands continue to grow at a rapid rate, so does the challenge of maintaining acceptable levels of data storage system performance.